Ab Initio Study of Gas Adsorption in Metal–Organic Frameworks Modified by Lithium: The Significant Role of Li-Containing Functional Groups

Metal–organic frameworks (MOFs) are promising materials for gas adsorption. Introducing metal cations, for example, lithium cations (Li⁺), in the framework is an effective way to alter the gas adsorption features of MOFs. In this work, Li⁺ carried by different functional groups was incorporated onto a benzene linker, which is one type of the most common liker used in MOF synthesis. The interactions between the Li-modified linkers and various gas molecules were studied using MP2 method. Compared to the original benzene ring, the structures and orbitals of Li-modified linkers were significantly changed toward the direction of enhancing gas adsorption. For nonpolar gas species (CH₄, H₂, N₂, and CO₂), the induced polarizations greatly enhance the interactions between gas molecules and MOF linkers. Particularly, the expanded binding energy differences of H₂/N₂, CH₄/CO₂, and N₂/CO₂ will make them easier to get separated. For polar gas species (H₂O, H₂S, SO₂, and CO), the electrostatic interactions between gas molecules and Li⁺ play a significant role in enhancing gas adsorption. The strong affinities between polar gases and Li-modified linkers denote that the binding sites around Li⁺ can be first occupied by polar molecules such as H₂O and SO₂ during the practical adsorption process. This can result in the reduced adsorption capacities of other gases, such as CO₂

Customized Electrolyte and Host Structures Enabling High-Energy-Density Anode-Free Potassium–Metal Batteries

Potassium shows great potential to replace lithium in energy storage for its high abundance and comparable energy density. However, issues including an unstable interphase, dendrite growth, and volume change restrict the development of potassium metal batteries, and so far, there is no single cure that works once and for all. Here an anode-free potassium metal battery is demonstrated by introducing a customized electrolyte and host structures that simultaneously promote efficiency, reversibility, and energy density. First, a diluted high-concentration electrolyte with fast kinetics and high stability triggers an inorganic-rich durable interphase. Meanwhile, a carbonaceous host containing narrowly distributed mesopores (MCNF) favors reduced surface area but enough inner space. Together, they achieve a high average Coulombic efficiency (CE) of 99.3% and an initial CE of 95.9% at 3 mA cm–2–3 mA h cm–2. Anode-free MCNF||Prussian blue (PB) potassium cells are delivered with 100 reversible cycles and a high energy density of 362 W h kg–1